arch/arm64/kernel/return_address.c

   1 /*
   2  * arch/arm64/kernel/return_address.c
   3  *
   4  * Copyright (C) 2013 Linaro Limited
   5  * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/export.h>
  13 #include <linux/ftrace.h>
  14
  15 #include <asm/stacktrace.h>
  16
  17 struct return_address_data {
  18         unsigned int level;
  19         void *addr;
  20 };
  21
  22 static int save_return_addr(struct stackframe *frame, void *d)
  23 {
  24         struct return_address_data *data = d;
  25
  26         if (!data->level) {
  27                 data->addr = (void *)frame->pc;
  28                 return 1;
  29         } else {
  30                 --data->level;
  31                 return 0;
  32         }
  33 }
  34
  35 void *return_address(unsigned int level)
  36 {
  37         struct return_address_data data;
  38         struct stackframe frame;
  39         register unsigned long current_sp asm ("sp");
  40
  41         data.level = level + 2;
  42         data.addr = NULL;
  43
  44         frame.fp = (unsigned long)__builtin_frame_address(0);
  45         frame.sp = current_sp;
  46         frame.pc = (unsigned long)return_address; /* dummy */
  47
  48         walk_stackframe(&frame, save_return_addr, &data);
  49
  50         if (!data.level)
  51                 return data.addr;
  52         else
  53                 return NULL;
  54 }
  55 EXPORT_SYMBOL_GPL(return_address);